Light source module using lasers as light source

1. Technical Field

The present disclosure relates to light source modules and, particularly, to a light source module using lasers.

2. Description of Related Art

Projectors generally include a light source, a color wheel, and a digital mirror device. Light rays emitting from the light source penetrate the color wheel and project onto the digital mirror device. The digital mirror device reflects the light rays under control of image signals to modulate the light rays into optical images. However, at present, the light source is typically a halogen lamp or three light emitting diodes (LEDs), directionality of the light rays is less than satisfactory and off-axis light rays do not project on the digital mirror device and are wasted, decreasing light usage efficiency.

Therefore, it is desirable to provide a light source module, which can overcome the limitations described.

FIG. 1 is a schematic view of a light source module in accordance with a first exemplary embodiment.

FIG. 2 is a schematic view of a light source module in accordance with a second exemplary embodiment.

Embodiments of the disclosure will be described with reference to the drawings.

FIG. 1 shows a light source module 100 , according to a first exemplary embodiment. The light source module 100 includes a double refraction prism 10 , an optical plate 20 , a first laser source 30 , a second laser source 40 , and a third laser source 50 . A first laser beam of a first color is emitted from the first laser source 30 , a second laser beam of a second color is emitted from the second laser source 40 , and a third laser beam of a third color is emitted from the third laser source 50 , the first, second, and third laser beams being mixed together into a mixed laser beam.

The double refraction prism 10 is rectangular, and is made of calcite crystal. The double refraction prism 10 includes an incident surface 11 and an emergent surface 12 opposite to and parallel with the incident surface 11 . The double refraction prism 10 has a fast axis 13 and a slow axis 14 . The fast axis 13 and the slow axis 14 extend from the incident surface 11 to the emergent surface 12 . The slow axis 14 is perpendicular to the incident surface 11 and the emergent surface 12 . The fast axis 13 intersects the slow axis 14 on the emergent surface 12 . An angle formed between the fast axis 13 and the slow axis 14 is θ. A distance between the incident surface 11 and the emergent surface 12 is H. The light rays polarized along an S polarization direction are transmitted along the slow axis 14 , and the light rays polarized along a P polarization direction are transmitted along the fast axis 13 .

The optical plate 20 is made of transparent material, and includes a reflection surface 21 and a transmission surface 22 opposite to the reflection surface 21 . The optical plate 20 is positioned adjacent to the double refraction prism 10 , and the transmission surface 22 faces the emergent surface 12 . The transmission surface 22 forms a 45 degrees angle with the emergent surface 12 . In the embodiment, red light rays and green light rays projected onto the transmission surface 22 are transmitted through the reflection surface 21 , and blue light rays projected on the reflection surface 21 are reflected by the reflection surface 21 .

The first laser source 30 is positioned adjacent to the double refraction prism 10 , and faces the incident surface 11 . The first laser beam emitted from the first laser source 30 is polarized along the S polarization direction. In the embodiment, the first laser beam is a red light ray.

The second laser source 40 is positioned adjacent to the double refraction prism 10 , and faces the incident surface 11 . The second laser beam emitted from the second laser source 40 is polarized along the P polarization direction. A distance between the first laser source 30 and the second laser source 40 is S, wherein tan θ=S/H. In the embodiment, the second laser beam is a green light ray.

The third laser source 50 is positioned adjacent to the optical plate 20 , and faces the reflection surface 21 . The third laser beam emitted from the third laser source 50 is polarized along the S polarization direction and the P polarization direction. In the embodiment, the third laser beam is a blue light ray. A projection direction of the third laser beam emitted from the third laser source 50 is parallel to the emergent surface 12 .

In use, the first laser beam emitted from the first laser source 30 transmits along the slow axis 14 , and the second laser beam emitted from the second laser source 40 transmits along the fast axis 13 . As the positional relationship of the double refraction prism 10 , the first laser source 30 , and the second laser source 40 satisfy the formula: tan θ=S/H, the first laser beam and the second laser beam are mixed on the emergent surface 12 , and are emitted from the emergent surface 12 along a direction perpendicular to the emergent surface 12 . The first and second laser beams emitted from the double refraction prism 10 project onto the transmission surface 22 and are emitted from the reflection surface 21 . A projection direction of the first and second laser beams transmitted from the optical plate 20 is perpendicular to the emergent surface 12 .

The third laser beam emitted from the third laser source 50 is projected onto the reflection surface 21 and is reflected by the reflection surface 21 . The projection direction of the third laser beam reflected by the reflection surface 21 is perpendicular to the emergent surface 12 . The first laser beam and the second laser beam transmitted from the optical plate 20 and the third laser beam reflected by the optical plate 20 are mixed together into the mixed laser beam.

FIG. 2 shows a light source module 100 a, according to a second exemplary embodiment. The difference between the light source module 100 a of the second exemplary embodiment and the light source module 100 of the first exemplary embodiment is that the reflection surface 21 a of the optical plate 20 a faces the emergent surface 12 and forms a 45 degrees angle with the emergent surface 12 .

The first and second laser beams emitted from the double refraction prism 10 project onto the reflection surface 21 a and are reflected by the reflection surface 21 a. The projection direction of the first and second laser beams reflected by the reflection surface 21 a is parallel with the emergent surface 12 . The third laser beam projects onto the transmission surface 22 and is emitted from the reflection surface 21 . The projection direction of the third laser beam transmitting from the optical plate 20 a is parallel with the emergent surface 12 . The first laser beam and the second laser beam reflected by the optical plate 20 a, and the third laser beam transmitted from the optical plate 20 , are mixed together into the mixed laser beam.

As the light source module 100 or 100 a uses lasers as the light source, the collimation of the light rays emitted from the light source is assured. The three color lasers are mixed together by the double refraction prism 10 and the optical plate 20 , 20 a, and the mixing accuracy of light source module 100 or 100 a is increased.

Particular embodiments are shown and are described by way of illustration only. The principles and the features of the present disclosure may be employed in various and numerous embodiments thereof without departing from the scope of the disclosure as claimed. The above-described embodiments illustrate the scope of the disclosure but do not restrict the scope of the disclosure.